AESC 2016 | 26-30 June 2016 – Adelaide Convention Centre
Regional metamorphism and alteration in the Nymagee area of New South Wales – a HyLogger studyDavid Tilley, Meagan Clissold, Peter Downes & Joel FitzherbertGeological Survey of New South Wales, Maitland and Londonderry
Nymagee ProjectLocation• centralpartoftheLachlanOrogen – southofCobar,
incentralNSW;including,theMountHopeTrough,Winduck Shelf,SouthernCobarBasin,MourambaShelf,Kopyje ShelfandRast Trough
Aims• tosystematicallydescribechangesinalteration
mineralogyforanumberofselectedmineralisedzones
• tocomparethealterationresponseofdifferingmineralisationstylestotheirhostrockpackage
• toassistmineralexplorerstobettertargetmineralisation
Mount Hope Trough
MountAllen
Great Central Mine
BackgroundResponse
• Quartz–muscovite–phengite–chloritewithzonesoffeldspar(bothK- andNa-richvarieties)
• Feldsparsconsistentwithhostrockmineralogy
GCS-1
DDH5
GCS-2
DDH3
DDHQDH4
GDDH5
GreatCentralSouth
GreatCentral
CometMinearea
QuarryHill
1km
Adjacenttomineralisedzone
• Chloritecontentincreases&changesfromFe- toMg-richchlorite
Ø zone40mwideatGreatCentral,10matQuarryHill
• AtGreatCentralSouth,whitemicabecomesmorephengitic• Analterationzoneassociatedwithapossiblebrecciaatthe
bottomofDDH5(GreatCentralminearea)hasnotbeenfullyassayed
Ø spectralresponseshowsanincreaseingoethiteandFe-richchlorite
Ø goethitesuggestsanincreaseinoxidisedsulfides inthiszone
Ø However,nogoethitedetectedbyXRD- thereforepoorlycrystallineironoxideslikely
Great Central Mine
Winduck Shelf
Manuka/Wonawinta
Manuka / Wonawinta
Theprimarysulfide-richmineralisationhostedbytheupperfossiliferous unitoftheBoothLimestone
Blackcarbonaceousshaleunit
Gossanousmaterial
ThuleGranite
Arkosic sandstone
N S E
Legend
Southern Cobar Basin
MayDay
May Day
Legend
Alteration
• Talc–carbonate(calcite),phengite,Mg-chloriteandbiotitewithminoramphibole
• K-feldspardestructive– oreformingfluidsMg-rich
315m
350m
Mouramba Shelf
Nymagee Coppermine
Nymagee Copper MineLithology
• Westfacingandsteeplydipping(80°)turbidite sequenceofmudstone,siltstone,sandstoneofthelowerAmphitheatreGroup.
Easternside- metamorphosedclay-richunit• Regionallymetamorphosedsiltstoneandclay-richsandstone– foliated.
• Sedimentarystructures- ripplecrossbedding,gradedbedding,cutandfillstructuresetc.
Westernside- quartzo-feldspathic unit
• Arkosic-lithicsandstone- derivedfromgraniticparentmaterial.Orezone
• Easternzone- relativelywide,Cu-rich.Thinmineralisedveinswithincleavageplanes.
• Westernzone- narrowandbrecciated,Zn-Pb-rich.
Nymagee Copper Mine
=mineralisedzone
Mg-chlorite
Fe-chlorite Fe-chlorite
Mg-chlorite
NMD053W1 NMD047
Chlorite composition
Nymagee NorthDistinctivelydifferentfromNymagee CopperMine• actinolite,grossular andsulfides withinaAg-richzone
at209m• anomalousCuandAupresent• separateorezonetothemainNymagee CopperMine
EastWest
Hera - Kershaws
NMD068
DD84KW1– anomalousCu
DD87KW3A– anomalousCuHRD003– oregradeCu
HRD019– narrowCu-richzone
White mica composition vs Cu
Hera - Kershaws Chlorite composition vs Cu
Fe-chlorite
Mg-chlorite
HRD003
Kopyje Shelf
Yellow Mountain
BackgroundResponse• Dependentonhostrock
mineralogy
• Quartz–K-feldspardominantwithvariableplagioclase,minorwhitemicaandvariableminorchlorite
• Consistentwithfelsicvolcanic/volcaniclastic hostrock
YD13 YD16
Yellow MountainAdjacenttomineralisedzone
YD16Changefromphengitic toanintermediatewhitemicacompositionabouta2.1mmineralisedzonewithveryminorMg-richchloritepresent
YD1329mwidemineralisedzonewhereK-feldsparislessabundantandthereisanincreaseinintermediatewhitemicaabundanceThesesubtlechangesareprobablyalteration-relatedbutthedominantspectralresponseintheseholesarehostrockrelated
YD13 YD13
YD16YD16
Mineral Hill
PearceParkerHill
EasternSouthernOreZone
BackgroundResponseThedepositishostedbyfelsicvolcanicrocks,limestoneandsiltstones
Mineral Hill - PearceKMHDD001 KMHDD003
AdjacenttomineralisedzoneAlterationconsistsofachlorite-quartz-whitemicaassemblagewithintensezonesofargillicalteration,someofwhichareassociatedwithmineralisation
Chlorite composition
Mineral Hill – Parker HillDistal• quartzandtalc,minorFe-chlorite,feldspar,
amphiboleandtracewhitemicaProximal• Mg-chloriteassociatedwithtalc• silicification andK-feldsparalteration
mainmineralisationzone
Mineral Hill - ESOZ
• Hostrockcomposedofquartz–chlorite–whitemica(notalc)• BothMgandFe-Mgchloritepresent• Al-OHabsorption feature(2175-2200nm)indicatespossible
paragonite (notvalidated)
Rast Trough
Browns ReefMineralisedzoneStandsoutfromthebackgroundspectralresponseduetoitsaspectralnature,adecreaseinthewhitemicaabundanceandlackofchlorite
Ø probablyduetosilicificationand/orsulfides
Nodiagnosticshiftinwhitemicacompositioncorrelatingwithmineralisation.
OutcomesHyLogger datacanbeusedto:• definethedegreeandextent
ofalterationproximalanddistaltomineralisedzones
• determinetheregionalmetamorphicgrade
• pointtowardshighergradezones,therebyfocussingexplorationeffortsHostrock1
Distalalteration
Proximalalteration
Mineralisation
Hostrock2
